/Engine/Source/Editor/SequencerCore/Public/MVVM/Selection/SequencerCoreSelectionIterators.h
// Filtered iteration is also supported for TWeakViewModelPtr<> types:
for (TViewModelPtrOutliner : Selection.Filter())
{
    // Only viewmodels that implement the IOutlinerExtension will be iterated
}
template<typename MixinType, typename KeyType> class TSelectionSetBase : public [UE::Sequencer::FSelectionBase](API\Editor\SequencerCore\MVVM\Selection\FSelectionBase)
TSet< KeyType >
SelectionSet